This invention relates in general to apparatus for applying closures to containers in which the closures must be threaded onto the containers. In particular, this invention relates to tightening mechanisms which exert a downwardly directed rotating force on closures in order to secure the closure onto the container.
Many systems are known for filling containers with a product, such as a liquid, and for automatically applying closures to the containers. Typically the containers are glass or plastic, and the closures are plastic or metallic. The closures are threaded, as are the necks or openings of the containers. Empty containers are sequentially fed through a filling station where the containers are filled, and then they are fed through a capping machine where the closures are applied. Rotary capping machines apply the closures or lids, and &ire the lids downwardly while rotating them to threadably secure the lids onto the container. High speed capping machines are capable of operating at rates of up to 750 containers per minute or higher. Closure application and tightening mechanisms are well known in the art.
A typical capping machine includes a closure applying apparatus having a torque applying capacity for threading the lids onto the containers. Also, the closure applying apparatus will have means, such as magnets, for holding the lids and depositing them on the containers. A clutch mechanism enables the lids to be tightened to a specified torque. Further, the closure applying apparatus has a means for driving the lid downwardly onto the container during the threading of the lids onto the containers. A commonly used method for driving the lid downwardly involves providing a cam assembly positioned along the path of the containers, and connecting the closure applying apparatus with a cam follower which tracks the cam groove in the cam assembly. The cam groove can be adapted to change the relative distance of the cam follower to the containers (i.e., move the cam follower closer to the container), thereby causing the closure applying apparatus to move downwardly so that the lid will be driven down onto the container.
A common practice in the industry is to provide a downwardly sloping portion in the cam groove to drive the lids onto the container. The slope of the cam groove is designed to fit the desired slope or pitch of the threads on the container. For example, if the lid has lug threads, the lid must descend fully onto the container during the time for about 1/4 of a rotation of the lid. For a continuous threaded closure, however, the lid must descend fully onto the container during the time for about 3 complete rotations of the lid. Various lids having different pitches require different descent times to apply the lids when the rotative rate or force is generally constant.
A problem with present day capping machines is that they have fixed cam grooves designed to apply lids having threads of a fixed pitch. In order to run the capping machine for both lug threaded lids and continuous threaded lids, the entire cam assembly, or at least the portion of the cam assembly having the lid descending slope, must be removed and replaced. The replacement portion will have an appropriate slope for the desired lid. Changing even a portion of the cam assembly requires extensive labor and machine downtime because of the complexity of the capping machine. Any improvement facilitating the changeover from one cam slope to another in capping machines would be a useful improvement in the art.